A certain library assesses fines for overdue books as follow

Day 1 : 0.1
Day 2 : Min{0.1x2,0.1+0.3}=0.2
Day 3 : Min{0.2x2,0.2+0.3}=0.4
Day 4 : Min{0.4x2,0.4+0.3}=0.7

And thus B

the total fine is increased by $0.30 or doubled, whichever results in a lesser amount - Keep the bolded phrases in mind .. it is quite confusing though ..
Day 1 - $.10
Day 2- $.10 *2 or $.10+$.30 (Whichever results in a lesser amount), hence its $.20
Day 3 - $.20*2 or $.20+$.30, $.40 as its lesser
Day 4 - $.40*2 or $.40+$.30, $.70 as this is lesser

So, Ans B.

Fines are already cumulative.

"For each additional day that the book is overdue, the total fine is ..."

Hope it's clear.

This one's tricky for sure.
Easy to fall for D.
Here's the solution
Day 1 = 0.1$
Day 2 ( Double or increase by 0.3$, chose the minimum one)
Option1: Double -> 0.1*2= 0.2$
Option2: Increase by 0.3$ -> 0.1+0.3 = 0.4$
Minimum one: 0.2$
Day 3
Option1: Double -> 0.2*2=0.4$
Option2: Increase by 0.3$ -> 0.2+0.3=0.5$
Minimum one: 0.4$
Day 4
Option1: Double -> 0.4*2=0.8$
Option2: Increase by 0.3$ -> 0.4+0.3=0.7$
Minimum one: 0.7$
hence the OA.

Hi ALL,

This question includes a 'conditional statement' that effects how you're supposed to handle each "step" in the math:

"for each additional day....., the total fine is EITHER increased by 30 cents OR doubled, whichever results in the LESSER AMOUNT."

Since we're asked to calculate a book that is 4 days overdue, we just have to consider each possible outcome on each day, then choose the one that leads to the "lesser amount"

Day 1: 10 cents

Day 2: 10 + 30 = 40 cents; 10(2) = 20 cents
20 cents is LOWER, so the fine is NOW 20 cents

Day 3: 20 + 30 = 50 cents; 20(2) = 40 cents
40 cents is LOWER, so the fine is NOW 40 cents

Day 4: 40 + 30 = 70 cents; 40(2) = 80 cents
70 cents is LOWER, so the final fine is 70 cents.

Final Answer:

GMAT assassins aren't born, they're made,
Rich

For the ease of calculation, I removed the decimal point from the question as well as from the OA's

1st day = 10

2nd day = 10*2 = 20 {10+30>10*2}

3rd day = 20*2 = 40 {20+30>20*2}

4th day = 40+30 = 70 {40+30 < 40*2}

Answer = B

HI dina98,

Many Test Takers become overly-obsessed with the implied 'level' of a question, when their focus should really be on whether the question was 'gettable' or not.

Ultimately, you should be measuring a question on a few key points:
1) Could you have gotten the question correct?
2) Was the work involved just too difficult (or was it actually really easy work)?
3) What could you do differently to make the overall process of dealing with the prompt easier (note-taking, organization, Tactics, etc.)?

The math involved in this prompt is remarkably low-level arithmetic, but the real 'test' here is how well you can organize the information involved and follow the instructions that the prompt gives you.

GMAT assassins aren't born, they're made,
Rich

Hi pra1785,

This question includes a 'conditional statement' that effects how you're supposed to handle each "step" in the math:

"for each additional day....., the total fine is EITHER increased by 30 cents OR doubled, whichever results in the LESSER AMOUNT."

Since we're asked to calculate a book that is 4 days overdue, we just have to consider each possible outcome on EACH day, then choose the one that leads to the "lesser amount"

Day 1: 10 cents

Day 2: 10 + 30 = 40 cents; 10(2) = 20 cents
20 cents is LOWER, so the fine is NOW 20 cents

Day 3: 20 + 30 = 50 cents; 20(2) = 40 cents
40 cents is LOWER, so the fine is NOW 40 cents

Day 4: 40 + 30 = 70 cents; 40(2) = 80 cents
70 cents is LOWER, so the final fine is 70 cents.

Final Answer:

GMAT assassins aren't born, they're made,
Rich

I am a little bit lost. Don't we have to add:

0.1+0.2+0.4+0.7


Thanks

Hi zonebp,

The prompt states that the we are supposed to use the fine each day that ends in the "LESSER AMOUNT." Based on the work that you did, on Day 3 you did NOT choose the fine that ended in the lesser amount (doubling .2 to .4 would be less than adding .3 to .2).

Most little mistakes can be avoided by taking the proper notes on your pad.

GMAT assassins aren't born, they're made,
Rich

On day 1, the fine is $0.10.
On day 2, we have two options:

1) 0.10 + 0.30 = $0.40
2) 0.10 x 2 = $0.20

Since option 2 is the lesser of the 2 fines, the total fine, as of day 2, is $0.20.

On day 3 we have two options:

1) 0.20 + 0.30 = $0.50
2) 0.20 x 2 = $0.40

Since option 2 is the lesser of the 2 fines, the total fine, as of day 3, is $0.40.

On day 4 we have two options:

1) 0.40 + 0.30 = $0.70
2) 0.40 x 2 = $0.80

Since option 1 is the lesser of the 2 fines, the total fine, as of day 4, is $0.70.

Answer: B

Hi kadamhari825,

The prompt tells us that one of two possible actions occurs each day:

"for each additional day....., the total fine is EITHER increased by 30 cents OR doubled, whichever results in the LESSER AMOUNT." This means that on certain days, we will ADD to the total and on other days, we will MULTIPLY the total by 2.... whichever results in the smaller total.

Since we're asked to calculate a book that is 4 days overdue, we just have to consider each possible outcome on each day, then choose the one that leads to the "lesser amount"

Day 1: 10 cents

Day 2: 10 + 30 = 40 cents; 10(2) = 20 cents
20 cents is LOWER, so the fine is NOW 20 cents

Day 3: 20 + 30 = 50 cents; 20(2) = 40 cents
40 cents is LOWER, so the fine is NOW 40 cents

Day 4: 40 + 30 = 70 cents; 40(2) = 80 cents
70 cents is LOWER, so the final fine is 70 cents.

GMAT assassins aren't born, they're made,
Rich

The catch here is that the fines are cumulative.

Fine on the first day is $0.1

Fine on the second day is 0.1*2 = $0.2 (as doubling gives us a lower value in comparison to fine increased by $0.30)

Similarly, fine on third day is 0.2*2 = $0.4 (as doubling gives us a lower value)

On the fourth day fine is 0.4 + 0.3 = $0.7 (as doubling gives higher value and thus we add $0.3)

Thus the fine overdue on fourth day is $0.4.
(option b)

D.S
GMAT SME

hey bunuel
I followed the wrong strategy earlier.
Do u have more questions like this to practice..
Thanx.

Day 1 fine: 0.1
Day 2 fine: 0.1*2 = 0.2
Day 3 fine: 0.2*2 = 0.4 or 0.2+0.3 = 0.5
Since 0.4 < 0.5, fine = 0.4

Day 4 fine: 0.4*2 = 0.8 or 0.4 + 0.3 = 0.7
Since 0.7 < 0.8, fine = 0.7

Correct Option: B

I still don't get this

day adding 0.30 doubling
1 0.10 0.10
2 0.40 0.20
3 0.70 0.40
4 1 0.80

Where am i going wrong?

This line in the question has killed me:
"the total fine is either increased by $0.30 or doubled."

What I have done:
Day 1: 0.1
Day 2: Double: 0.2
Day 3: Add 0.3
Day 4: Add 0.3
Then add all of them: 0.1+.2+.3+.3 = 0.9
The test writer has successfully tricked me to pick this incorrect option D by just one term in question prompt "Total Fine"
Please advise how to avoid such traps.